Abstract Body (Do not enter title and authors here): Background:
Aortic aneurysms account for ~10,000 deaths annually in the USA. Oxidative stress is implicated in both abdominal (AAA) and thoracic (TAA) aneurysm formation, but the mechanisms are incompletely understood. We used a chemogenetic approach to modulate oxidative stress in the vascular wall by creating a transgenic mouse (DAAO-TG^Tie2) that expresses yeast D-amino acid oxidase (DAAO) driven by the endothelial Tie2 promoter. DAAO generates the reactive oxygen species hydrogen peroxide from D-amino acids. Vascular tissues contain L-amino acids, so yeast DAAO is quiescent until DAAO-TG^Tie2 mice are provided with D-amino acids. Here we characterize the cellular and molecular consequences of vascular oxidative stress in DAAO-TG^Tie2 mice.
Hypothesis:
Chronic oxidative stress in the vascular wall causes arterial dysfunction.
Aim:
To characterize the phenotype of DAAO-TG^Tie2 mice after oxidative stress induction in vascular endothelium.
To identify the mechanisms whereby vascular oxidative stress causes arterial dysfunction and hypertension.
Methods:
Systolic blood pressure and aortic sonography were measured weekly in D-alanine-fed DAAO-TG^Tie2. Proteomic analyses were used to identify mechanistic targets, which were validated using biochemical and immunohistochemical methods.
Results:
D-alanine-fed DAAO-TG^Tie2 mice develop systolic hypertension and abdominal but not thoracic aortic aneurysms; treated mice die in >3 months with burst abdominal aortic aneurysms. Transgene expression is similar in abdominal and thoracic endothelium. Levels of oxidative stress markers (oxidized proteins, lipid, and DNA) were similar in thoracic and abdominal aorta. Proteomic analyses established phenotypic switching in abdominal but not thoracic aorta, and also revealed activation of the oxidant-activated kinase ASK1 and of the MAP kinase cascade in abdominal but not thoracic aorta. Immunoblot analyses showed a marked decrease in JNK1 phosphorylation by phosphatase DUSP3 and an increase in vascular KLF4, leading to phenotypic switching of contractile to synthetic VSMCs.
Conclusion:
Chronic chemogenetic oxidative stress induces hypertension and abdominal aortic aneurysm formation caused by KLF4-dependent VSMC phenotypic switching.